The surgical treatment of inveterate fractures of the acetabulum.

Any fracture of the acetabulum which is not adequately treated within 3 weeks poses a considerable surgical problem. Reduction is difficult, callus has already begun to form between the displaced fragments, and the risks of complications are therefore increased. Our material consists of 35 cases, subdivided into 18 fractures submitted for treatment between 3 and 12 weeks after injury, and 17 fractures submitted for treatment beyond the 12 week limit. In the first group the incidence of complications (ischaemic necrosis, arthrosis, infection) was high; satisfactory results were obtained only when the fracture was of the simplest type. In the second group, malunion had to be accepted, and treatment was concerned solely with improving function by correcting malposition and relieving or eliminating pain. The surgical methods adopted depended on the circumstances: corrective osteotomy, arthrodesis or total prosthetic replacement.

Comparative actions of four aminoglycoside antibiotics on the vestibular function in guinea-pigs.

This study was designed to assess the actions of 4 representative aminoglycoside antibiotics on the vestibular functions in guinea-pigs as evidenced by the measurements of the vestibulo-ocular reflex (VOR) either in the horizontal (HVOR) or in the vertical plane (VVOR). VOR responses were evaluated over a wide range of stimulation frequencies prior to and after 10 and 18 days of a multiple dose regimen with dibekacin (150 mg/kg), gentamicin (100 mg/kg), netilmicin (150 mg/kg), tobramycin (100 mg/kg) or saline. All drugs or saline were given intramuscularly twice a day. The labirinthine function was found to be differently impaired by drug administration. Gentamicin induced severe vestibular impairment, which had early onset. Dibekacin greatly reduced all VOR responses, but changes occurred after a longer period of time. Tobramycin and netilmicin induced slight vestibular impairment only after 18 days of treatment. Tobramycin affected both HVOR and VVOR responses at the high frequencies, while netilmicin impaired only the HVOR. Histological examination of vestibular epithelia was conducted by using the Scanning Electron Microscope (SEM). Gentamicin and dibekacin greatly damaged both the cristae of semicircular canals and utriculi, structures which are involved in the generation of VOR responses. Conversely, tobramycin provoked damages only in the cristae of semicircular canals and netilmicin did not affect the vestibular sensory epithelia. These findings indicate that each aminoglycoside produces characteristic actions on the vestibular function which depend on the damage distribution in the labirinthine structures. Among the aminoglycoside examined, netilmicin appears to possess the lowest potential for producing impairment of the vestibular function.

Vestibulo-ocular reflex (VOR) in guinea pigs. Impairment induced by aminoglycoside antibiotics.

The vestibulo-ocular reflexes (VORs) were studied in guinea pigs receiving daily administration of aminoglycoside antibiotics. The vestibular epithelia were also examined by scanning electron microscope technique (SEM). The treatment with aminoglycosides led to varying degrees of VORs according to (i) the type of aminoglycoside drug; (ii) the duration of the treatment and, (iii) the sensitivity of the various vestibular receptors. Gentamicin caused an earlier and severe reduction of the VOR gain. Dibekacin also caused evident damage, but the onset of its action was delayed. Both drugs affected mainly the vertical responses. Tobramycin and netilmicin altered the VORs slightly. Histological examination revealed damage to the sensory epithelia corresponding to the observed VOR impairments.

Stoichiometry of hemolysis by the polyene antibiotic lucensomycin.

The stoichiometry of hemolysis by the polyene antibiotic lucensomycin was investigated. It appears that hemolysis occurs only when a relatively high fraction (probably between 15 and 40%) of the cholesterol sites in the erythrocyte membrane have combined with the polyene. Also in phospholipid-cholesterol vesicles the increase of permeability requires occupancy of 40-50% of the existing cholesterol sites. As for the possible cooperative effect in the hemolytic process, it is probable that several (at least 9-10) lucensomycin-cholesterol adducts must interact on each side of the membrane to form an aqueous channel; the distribution of these adducts in the erythrocyte membrane occurs, however, apparently at random.